The present invention relates to a new and improved construction of a roller apron or strand guide arrangement for the withdrawal and/or straightening region of a continuous casting installation for strands.
Generally speaking, the roller apron for the withdrawal and/or straightening region of a continuous casting installation for strands as contemplated by the present invention is of the type comprising two roll or roller tracks which are subdivided into sections or segments, wherein there are provided for each roll track two rolls. The rolls of each track section are mounted upon a respective traverse or yoke, and the one traverse is secured to a frame and the other traverse is hingedly connected to piston rod heads of stationarily arranged pressurized fluid medium cylinders and the piston rod heads are operatively associated with guides at stands, these guides extending transversely to the roll track.
In a prior art straightening machine of a continuous casting installation for strands, for instance as disclosed in German Patent Publication No. 2,023,319 and the corresponding U.S. Pat. No. 3,707,184, granted Dec. 26, 1972, upper and lower traverses or yokes are attached to pivot pins arranged between two roll bearings in the manner of a balance or rocker. Each pivot pin of the upper traverse is secured in a piston rod head of a pressurized fluid medium cylinder arranged in the frame. At the frame there are anchored to both sides of each pressurized fluid medium cylinder two stands or uprights between which there is guided the piston rod head of the pressurized fluid medium cylinder. The upper traverse or yoke is elevationally adjustable in this manner and is pivotable about its center.
This pivotability of the upper traverse with the prior art straightening machine, during a deviation or shifting of the one roll in consequence of the tilting or rocker movement of the other roll, presses into the still plastically deformable strand, so that there are formed localized rolling actions at the cast strand resulting in deviations from its reference or set thickness value. The stands located at the central region of the traverse hinder both the visual and physical access at this location of the continuous casting installation. A design using pivot pins arranged between the roll bearings requires a large spacing of the rolls from one another. A more compact arrangement of the rolls would be associated with appreciable structural modifications and difficulties as concerns maintenance of the equipment. A further shortcoming of the state-of-the-art construction resides in the fact that with an inclined position of the upper traverse there arises an appreciable lateral deflection in the direction of the neighboring traverse or yoke. To prevent abutment of neighboring upper traverses or their rolls or bearings, it is therefore necessary to provide a certain spacing between the traverses or yokes. This constitutes a further reason why with the described prior art construction there cannot be realized a uniform close spacing of the rolls as is needed for modern day continuous casting installations.